Solitary fibrous tumor (hemangiopericytoma) (histology)

Case contributed by Frank Gaillard


Middle aged adult presenting with a large durally based tumor.

Slides of a solitary fibrous tumor (previously hemangiopericytoma) demonstrate a highly cellular tumor with sparse background reticulum and numerous branching thin-walled vessels and frequent mitoses. Areas of necrosis are visible (figure 4). This is consistent with a grade III hemangiopericytoma pattern tumor. 

Ideally, the diagnosis would be confirmed with STAT6 immunohistochemistry, as well as CD34 and vimentin. 

Note: Due to molecular/genetic similarities hemangiopericytomas are no longer recognized as distinct entities. Instead, they represent cellular higher-grade solitary fibrous tumors. In the 2016 revised 4th Edition of the WHO classification of CNS tumors, they were grouped together under one diagnosis (solitary fibrous tumor/hemangiopericytoma), and in the 2021 5th edition the term hemangiopericytoma was dropped entirely. 

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